Brake for vehicles



June 10, 1930. F. T. BURGESS AL BRAKE FOR VEHICLES Filed Aug. 29, 19 8 my M W m 4: W wm/ m 5 ,4 m W 4 7 m Z & vw

Patented June 10, 1930 STATES FATE N T OFFICE FREDERICK T-ASKER BURGESS. AND CHARLES WELLIAIVIv SEXVELL, OF CRICKLEWOOD, ENGLAND, ASSIGNORS F GNE-TEIRD'TO BENTLEY IYIOTORS LIIVIITED, OF' CBICKLE- WOOD, ENGLAND, A BRITISH COMPANY BRAKE FOR VEEICLES Application filed. August 29, 1828, Serial No. 302,816, and. in Great Britain February 21,

This invention relates to brakes of the internalexpanding kind having a forward shoe which is applied bythe cam and is connected by a floating pivot with a rearward shoe. Such brakes are generally known as servo shoe brakes.

A defect with this type of brake is that the two shoes are only located by the applying cam for the forward shoe and the abutment for the rear shoe, which are close together, and consequently the shoes are liable to swing edgewise on rough roads and strike the drum at points about 90 degrees around the circumference from the location points.

To overcome this there is frequently employed a stop which engages the rear shoe towards the floating pivot end, but this stop requires adjustment every time the brake is adjusted in order that movement in the off position of the rear shoe may not become excessive as the lining or drum wears.

The object of the present invention is to provide a simple system by which the foregoing defect is avoided, and as a result no adjustment is necessary until the brake requires re-lining.

in the accompanying drawings, which show a preferred construction,

Figure 1 is an elevation, partly in section, showing the brake applied, and

Figure 2, on a larger scale, is a fragmentary section on the line 11-11 of Figure 1.

In the construction shown, the applying cam 2 is at the top of the brake in engagement with the forward shoe 3 and the abutment forming the location point for the rear shoe 4: is close to it. Preferably the rear shoe terminates in a peg or roller 5 which is held by the usual spring 6 against an ineflective, or

practically ineffective, surface 7 on the applying carn, so that comparatively little torque positive or negative is applied to the cam by the shoe 4:.

The applying portion of the cam may be a nose 8, of such an angle to give the most uniform mot-ion, which is adapted to bear against the end of the forward shoe. At the bottom of the brake is the floating pivot 9 and this is supported by the swinging link 10 pivoted at 11 to the anchor plate 12. The forward shoe terminates in a jaw 13 which half embraces the pivot pin, whilst the other half of the pivot pin is embraced by a jaw 1s" on the rear shoe, the two being held together by a spring 15 at each side of the swinging link and connecting the two shoes. If desirable, clearance may be provided for the pin in the jaws. hen the brake lining is unworn, the

swinging link 10 hangs vertically, or approximately so, from the anchor plate, and integral with the'link is an arm 16 which preferably is radial to the axis of the pivot pin and which projects towards the forward shoe and is connectedwith it by a pin-and-slotor similarjoint.

This armis slightly resilient, and it may terminate in a rounded-end 17 or roller'which engages a slot 18in a stud lfi) which is carried non-rotatably as at 20 by the forward shoe 3 and whose position can be adjusted'along a slot21-therein. The direction of this slot is preferably at right angles to the normal'p'osition of. the arm 16 and is approximately directed toward the. axis of the applying cam 2. The stud 19 can be locked in any desired position in the slot 21, and for access to the locking'nut 22'anaperture 23 is. formed in the anchor plateof the brake, this being closed by alight cover 24;.

In setting the adjustment, the: lock nut 22 is slackened and. the brake fully applied, which causes both shoes to bear against the brake drum. 25. The lock nut is then tightened up, after which no further adjustmentis necessary unless the brake is dismantled or one of the linings altered;

then the brake is applied, the forward shoe 3 tends to travel round with" the drum in the usual manner in the direction of the arrow 26, and'applies the rear shoe bythrust through. the floating pivot also: in the usual manner. It may be that in this'operation the arm 16""may bend slightly owingrto tlrepath'.

cally the same as that which exists in ordinary brakes of this type.

If, however, the position of the applying cam 2 is adjusted angularly to take up backlash as the brake wears such movement will obviously alter the OE position of the for ward shoe, and this in turn, through the action of the slot 18 upon the resilient arm 16, will move the floating pivot and push the rear shoe 4 slightly closer to the drum. In this way the off position of the rear shoe is controlled and swinging of the two shoes about the location points at the top of the brake is prevented by means of the flexible arm and its engagement with the guide slot on the shoe 3. g

It is preferred that the contact between the rear shoe. and the applying cam member (which, as shown at 7, is eccentric at the hack) should be such that, as the cam is moved to apply the brake, it moves the rear shoe slightly in a contrary direction to that of usual rotation of the brake drum. This prevents excessive servo action and gives the additional amount of take up of the clearance between the rear shoe and brake drum, and also assists the brakingiefl'ect when the vehicle is travelling backwards. lln most servo shoe brakes the braking effect when travelling backwards is considerably less than when travelling forwards.

By this invention simple means is provided for locating the rear shoe and for enabling a single adjustment of the brake to do all that is required.

What we claim asour invention and desire to secure by Letters Patent of the United States is I 1. In an internal expanding brake, the combination of a forward shoe, a rearward shoe, a floating pivot connecting the two tion which is at right angles to the normal position of the arm, substantially as set forth.

, ,4. A brake as claimed in claim 2, in which movement of the guides to adjust them is approximately on a line directed to the axis of the applying cam, substantially'as set forth. 5. In an internal expanding brake, the

combination of a forward 'shoe, a rearward shoe,

In testimony whereof we have signed our names to this specification.

FREDERICK TASKER BURGESS. CHARLES WILLIAM SEWELL.

shoes, means for applying said forward shoe,

a swinging link supporting said floating pivot, an arm on the swlngmg link whlch has a sliding engagement with the forward shoe so arranged that there is no interference with the servo action of thebrake, substantially as set forth. a

2. In an internal expanding brake, the

combination of a forward shoe, a rearward shoe, a floating pivot connecting the two shoes, means for applying said forward shoe, a swinging link supporting said floating pivot, an arm carried by said swinging link slidably engaging in guides provided on the forward shoe, and these guides are adjustable for position sideways, and a connection be tween said arm and said forward shoe such that the position of said link and thus of said floating pivot varies the forward shoe, substantiallyas set forth.

3. A brake as claimed in claim2, in which 1 guides are formed in a stud which is carried non-rotatably by the forward shoe and is adjustable along a slot therein in a direcwith the position'of' 

